The present invention relates to a blade pushing device of a cutting knife wherein the spring member has two ends contacting against two insides of the body member so as to prevent the spring member from being fatigue fast.
A conventional cutting knife 10 is shown in FIGS. 1 and 2 and in U.S. Pat. No. 6,226,873. A slider 13 is slidably engaged with the slot 111 of the holder 11. A blade 12 is connected to the base plate, of the slider 13 and a leaf spring 133 is received in a chamber 131 A of a body member 131 of the slider 13. The leaf spring 133 includes a protrusion 133A that retractably extends through a notch of the body member 131 so as to be engaged with one of the recesses 111A defined in the inside of the slot 111. An operation member 132 is movably mounted to the body member 131 and has a wedge-shaped notch 132A which may push the protrusion 133A of the leaf spring 133 downward to disengage the protrusion 133A from the recess 111A so that the blade 12 can be moved till the protrusion 133A is engaged with another recess 111A. The two ends of the leaf spring 133 have no stop means to limit their deformation and shifting so that the deformation of the leaf spring 133 is not under control and this makes the leaf spring 133 to reach its limitation of fatigue more quickly than expected.
The present invention intends to provide an improved blade pushing device for a cutting knife and the two ends of the spring member are stopped by two insides of the body such that the deformation of the spring member can be well controlled.
The primary object of the present invention is to provide a cutting knife that has a spring member received in a base member which is slidably engaged with the slot in the holder, a spring is biased between an inside of the wall and the reverse side of the protrusion of the spring member so as to provide a force to engage the protrusions with one of the recesses defined in one of two sides of the slot.
Another object of the present invention is to provide a cutting knife wherein the spring member has two end portions which contact against the insides of the wall so as to limit the deformation n of the spring member when the protrusion of the spring member is pushed to disengage from the opening of the wall of the base member.